1. Field of the Invention
This invention relates to a printing device, more particularly, to a device with an ink ribbon enclosed within a case, which is so constructed that the ribbon is pulled out through an opening thereof to be fed outside and then, drawn into the inside chamber thereof through another opening. Moreover, this invention relates to a printing device for printing onto a printing sheet placed on a platen via a printhead mounted on a carriage especially when the carriage laterally moves on a guide member.
2. Prior Art
In the conventional printing device of the aforementioned type, ribbon guiding members such as rollers are attached along the threading path of a ribbon so that the ribbon is properly advanced.
Generally, upon printing by means of a conventional printing device, an outer running part of an ink ribbon is pressed against the platen by a printhead so as to type on a printing sheet placed on the platen. Therefore, with such device of the above type, the running part of the ink ribbon is kept tense during printing. However, after printing, when the printhead returns to its original position, the tension in the running part of the ink ribbon is released, resulting in a twist of the ink ribbon due to a shift thereof occurring on the ribbon guiding member such as a roller.
In another known type of the prior art, a support arm, with a printhead fixed to the nose end thereof, is attached to rotate a base end of a carriage. When not printing, the end of the support arm is positioned apart from a platen. When printing, on the other hand, the nose end of the support arm is rotated to a position adjacent to the platen, resulting in printing action via the printhead. However, using the printing device of the above type, when the nose end of the support arm is rotated to a position in the vicinity of the platen, the printhead fails to be accurately positioned to the predetermined printing line on the platen; this is due to such factors as play in the support arm attached to the carriage, or to the deformation of the carriage per se. Another problem has occurred that the printing device, including the correction mechanism, fails in the correction operation because the printhead is not accurately positioned for correcting on the printing sheet. The aforementioned troubles during printing or correcting by means of the conventional printing device have frequently occurred when the carriage employed in the device is formed from synthetic resins.